I do not have sliding problems, now that I lowered by car. I have to use pieces of 2x8's at the beginning of the ramps, because the front spoiler hits the ramp before the tire does. Once I did that, it solved my sliding ramp issue.

The only problem with nailed board type ramps is that they are HEAVY and usually very long to get the stepped lift you need. But on the plus side they are very inexpensive and very strong.

Not necessarily true I built a set for my lowered GTI as I couldnt get up my steel ramps anymore. The wood ones are lighter and shorter (in height and length), they don't go up as high but they are high enough to get under and change the oil.

I would recommend getting a good pair of jack stands and a floor jack. There is usually a center point at the front of the car where you can lift the entire front end at once which allows you to put the jack stands in place.

I used to have steel ramps that I thought worked well, I had them slip on me once and almost damaged the underside of my car. Never used them again, not worth the risk.